Rapid determination of short chain carnitines in human plasma by electrospray ionisation-ion trap mass spectrometry using capillary electrophoresis instrument as sampler

A capillary electrophoresis apparatus was used as sampler for flow injection analysis (FIA) in tandem mass spectrometry of L-carnitine and its acetyl- and propionyl-metabolites in human plasma. The capillary electrophoresis instrument was coupled to the ion trap mass spectrometer by an electrospray ionization coaxial sheath liquid interface. The electrophoresis capillary introduced the sample directly into the source by applying a prolonged sample injection. The use of the capillary electrophoresis apparatus miniaturised the FIA procedure, substantially reducing the quantities of solvents and samples used, and allowed rapid automated sequential analyses. The method was optimised and validated using a dialyzed human plasma matrix. The plasma samples were analysed after a simple, rapid deproteinisation procedure with acetonitrile and diluted 70 times before direct injection into the mass spectrometer for product ion scan MS/MS analysis in positive ionisation. The total analysis time was 5 min, including capillary preconditioning and acquisition time (3 min). The method was sensitive, allowing the determination of L-, L-acetyl- and L-propionyl-carnitines at 140, 14 and 3.6 nM concentrations (injected values) corresponding to lower limit of quantitation values in plasma of 10, 1 and 0.25 microM, respectively. The method was processed for full validation and applied to the analysis of L-carnitine and its short chain derivatives in human plasma samples.     

A Simple Strategy for Easily Assembling 3D Printed Miniaturized Cells Suitable for Simultaneous Electrochemical and Spectrophotometric Analyses

A rapid and user‐friendly approach is here presented for assembling smart and versatile platforms for simultaneous electrochemical and spectrophotometric measurements. They consist of an optically transparent pencil‐drawn electrochemical cell, including reference, counter and working carbon electrodes, assembled on flexible PVC supports, exploiting a commercial desktop digitally controlled plotter/cutter. This cell is installed on a U shaped 3D printed polylactic frame where a second transparent window consisting of an unmodified PVC layer was also applied. After optimization of the fabrication procedure, the electrochemical and optical characterization of the assembled miniaturized platforms was performed by using aqueous electrolytes and potassium hexacyanoferrate(II) as redox probe. These devices were then tested by a proof‐of‐concept direct and simultaneous electrochemical and spectrophotometric quantification of a commonly used food dye (Brilliant Blue, E‐133) in soft‐drinks and candies. Spectrophotometric and electrochemical determinations can be performed at the same time, providing simultaneous information and enabling a concomitant comparison and validation of the results obtained.     

Smart network based portfolios

Annals of Operations Research - In this article we deal with the problem of portfolio allocation by enhancing network theory tools. We propose the use of the correlation network dependence...     

SiO2-Coated ZnO Nanoflakes Decorated with Ag Nanoparticles for Photocatalytic Water Oxidation

Many strategies have been adopted to improve the photoinduced features of zinc oxide nanostructures for different application fields. In this work, zinc oxide has been synthesised and decorated by plasmonic metal nanoparticles to enhance its photocatalytic activity in the visible range. Furthermore, an insulating layer of SiO₂ has been grown between the surface of zinc oxide nanoflakes and silver nanoparticles. A synthetic procedure that allows the accurate modulation of the insulating layer thickness in the range 5–40 nm has been developed. Evidences highlight the crucial role of the SiO₂ layer in dramatically increasing photocatalytic water oxidation promoted by the nanostructure under both UV and visible illumination. An ideal thickness value of about 10 nm has been demonstrated to guarantee the plasmon-induced resonance energy-transfer process and to quench the Förster resonance energy-transfer mechanism; thus, optimising the local surface plasmon resonance effect and water oxidation properties.     

Amperometric Sniffer Based on Electrodes Supported on Ion‐Exchangers for Monitoring the State of Turning Rancid of Lipids

A porous gold electrode supported on one face of an ion‐exchange membrane, acting as a solid polymer electrolyte (SPE), is proposed as an amperometric sniffer for monitoring the aldehyde content in the headspace in equilibrium with lipid samples, in order to gain indication of their state of turning rancid It was used as a detector for a flow injection system in which aldehydes were injected, after preconcentration by solid phase microextraction on a SPME fiber from the gas phase standing above thermostated samples and subsequent desorption by heating. Repeatable (±4.5%) sharp peaks were detected over a wide linear concentration range (0.5–200 ppm). A detection limit of about 0.03 ppm was inferred for a signal‐to‐noise ratio of 3, referred to hexylaldehyde (used as prototype) dissolved in squalene or vegetable oils samples. This approach was applied to the determination of volatile aldehydes from some partially oxidized cereal oils and the results found were compared with both the corresponding peroxide values and their aldehyde content determined by a conventional spectrophotometric method.     

Synthesis of Copper(I) Complexes with Ketimide and Hydrazide Ligands

Copper(I) chloride reacted with lithium ketimides to form tetrameric homoleptic copper(I) ketimide complexes, [Cu(N=CR₂)]₄, where R = t-Bu or Ph. Mesityl copper reacted with excess 1-trimethylsilylmethyl-2,2,-dimethylhydrazine to give the mixed ligand complex (2,4,6-C₆Me₃H₂)Cu₄[N(SiMe₃)NMe₂]₃. Single-crystal X-ray crystallographic studies revealed that the three complexes have eight-member ring structures in which the ring has a hinged or butterfly shape. Although an eight-member ring structure is common for copper(I) amido, alkyl, and aryl clusters, the structure of [Cu(N=C-t-Bu₂)]₄ is unusual because the hinge angle is significantly smaller than is common, resulting in short Cu···Cu contacts compared to related complexes.     

The effect of hydrogen bond on the vibrational dynamics of genistein free and complexed with β‐cyclodextrins

Inclusion, or host–guest, complexes are supramolecular assemblies in which two or more molecules hold together and organize by means of intermolecular noncovalent bonds. In the pharmaceutical field, inclusion complexation of drugs with unsubstituted and derivative β‐cyclodextrins (β‐CDs) has proven to be a successful method to improve the dissolution of water insoluble drugs. Genistein (Gen), an isoflavone constituent of Onodis spinosae radix, turned out to be a suitable guest molecule for the encapsulation into β‐CD, resulting in a significant improvement of its aqueous solubility. In the present study, the modifications of the vibrational spectrum of Gen caused by its inclusion into β‐CDs cavity have been characterized by means of Raman scattering experiments. These changes have been interpreted by comparing the experimental data with the vibrational wavenumbers and Raman intensities obtained by simulation for the free and complexed guest molecule. Following this strategy, we have obtained a deeper understanding of the host–guest interactions involved in the formation and stabilization of the complexes, with particular regard to the role played by the guest chemical groups, as well as to disentangle the effects directly related to the complexation process from those ascribed to other factors, such as formation of intra‐ and intermolecular hydrogen bonds. Copyright © 2009 John Wiley & Sons, Ltd.     

Radical reduction of aromatic azides to amines with tributylgermanium hydride

[reaction: see text] Aromatic azides are inert toward tributylgermanium hydride under thermal conditions in the absence and in the presence of a radical initiator but in the presence of catalytic amounts of benzenethiol undergo fast reaction, yielding reduced anilines and 2-germylated derivatives in high overall yields.     

On Neumann boundary control problem for ill-posed strongly nonlinear elliptic equation with p-Laplace operator and $$L^1$$L1-type of nonlinearity

Ricerche di Matematica - In this paper we study an optimal control problem for the mixed Dirichlet–Neumann boundary value problem for the strongly non-linear elliptic equation with p-Laplace...